Using the diet of fish to reflect spatial patterns of their benthic prey

The ability to efficiently implement ecosystem-based fisheries management is largely dependent on data availability. As invertebrates are not included in routine monitoring programmes, data should be collected by different approaches. We assessed whether fish could be suitable biological samplers of benthic invertebrates in the Eastern English Channel by comparing spatial distributions of Galatheidae, Portunidae and Porcellanidae found in digestive tracts (DTs) from a fish survey (Channel Ground Fish Survey), and in a dedicated benthos survey (Eastern English Channel Benthic Survey, ECBS). We found a significant spatial match between the distributions of Porcellanidae, Galatheidae and Portunidae found in fish DTs, and the ECBS occurrence-based maps. The strongest overlap was found for Galatheidae. Spatial distributions of Porcellanidae based on fish DTs better overlapped those derived from dedicated benthos surveys when we assumed these prey to also be consumed in the neighbouring spatial units to where fish were sampled. This might reflect the relatively high mobility of the dominant predators of Porcellanidae (e.g. Mustelus asterias, Scyliorhinus canicula). Overall, this study demonstrated that fish diet sampling can provide valuable information on the spatial distribution of benthic organisms.